This invention relates to a boot that engages a caliper to hold a seal in a bore that retains an actuation piston for a disc brake.
In disc brakes, it is common for a caliper to straddle a rotor that is fixed to an axle of a vehicle. The caliper is located on a yoke that is secured to the housing of the vehicle and has a bore therein which holds an actuation piston. A seal located in a groove in the caliper engages the piston to seal the bore and define an actuation chamber. A first friction member is connected to the actuation piston and a second friction member is connected to an arm extending from the caliper. The first and second friction members are located on opposite sides of the rotor and when pressurized fluid is supplied to the actuation chamber, the piston and caliper move in such a manner that the first and second friction members engage the rotor to effect a brake application. The following U.S. Patents are illustrative of disc brake and their corresponding functional operation: U.S. Pat. Nos. 3,113,643; 3,421,604; 3,442,356; 3,868,001; 3,912,051; 3,998,466; 4,530,423; 5,660,253; 5,700,067; 5,713,435; 5,826,681; 5,845,747; 6,000,506; 6,044,936; 6,073,733; and 6,135,245. All of the disc brakes disclosed by these patents while possessing different structural components operate in a manner to effect a brake application in a manner as describe above. It should be noted that in of the above patents a disc brake is disclosed as having a groove located in the bore of the caliper to retain a seal that engages the piston to seal the actuation chamber. In the manufacture of the caliper the groove is machined in the bore and as a result all material removed from the housing to create the groove must be removed before the seal is inserted in the groove. Unfortunately, it is possible that some material in the form of chips may be retained in the groove and when the seal is inserted into the groove some damage may occur. The damage may take the form of a cut to the seal or the seal may not fully engaging the bottom of the groove and as a result a leak path could occur for pressurized fluid presented to the actuation chamber with the environment. In addition, during the assembly of this type disc brake, a substantial force is required to insert the piston into the bore and the seal could actually be rolled or twisted which also could result in a leak path as described above.
A primary object of the present invention is to simplify the manufacture of a caliper for a disc brake by reducing the possibility of retention of material from a machining process in a groove which could later contribute to the development of a leak path and to provide a piston and associated seal-boot assembly which is easily inserted into a bore to form a sealed actuation chamber for a disc brake.
In more particular detail, the disc brake of the present invention includes a caliper that straddles a rotor and is retained on a yoke attached to a vehicle. The caliper has a bore therein and with a piston defines an actuation chamber. A seal and bearing arrangement that is connected to the caliper engages the piston to seal the actuation chamber from the surrounding environment. A first friction member is attached to the piston and a second friction member is attached to an arm that extends from the bridge of the caliper. When pressurized fluid from a source is presented to the actuation chamber, the pressurized fluid acts on the piston and caliper to move the first and second friction members into engagement with the rotor to effect a brake application. The disc brake is characterized by the bore in the caliper having a first diameter separated from a second diameter by an annular shoulder and a groove located in the second diameter to create a step adjacent the annular shoulder and by a boot which holds the seal against the annular shoulder. The boot has a cylindrical body with a first end with a radial outward projection that extends therefrom and a second end with a radial inward lip that extends therefrom. The seal is initially placed on the peripheral surface of the piston and the boot is thereafter placed adjacent the seal. A force is applied to the second end of the boot to move the first end of the boot into engagement with the seal and the second diameter of the bore. As the boot moves the seal into the bore, the outward radial projection of the boot engages the second diameter of the bore and flexes toward the piston. The force on the boot moves the seal past the annular groove and onto the step to bring the seal into engagement with annular shoulder. When the seal engages the annular shoulder, the resiliency of the boot causes the radial outward projection on the first end snaps into the annular groove and locks boot and correspondingly the seal onto the caliper.
An advantage of the disc brake of the present invention resides in the ease whereby a piston and seal-boot assembly is placed in a bore to seal an actuation chamber of a disc brake.
A further advantage of the disc brake resides in a boot that holds a seal in a bore that engages a piston to seal the bore and define an actuation chamber within the housing of a caliper.